Nelson, an Air Force captain, was heading for his day shift on a new kind of job, one that could require him to kill another human being 7,500 miles away.
Seated in a padded chair inside a low, tan building, he controlled a heavily armed drone aircraft soaring over Afghanistan. When his shift ended, he drove 40 minutes back through the desert to the hustle and neon of Las Vegas.
Drone pilots and crews are the vanguard of a revolution in warfare, one that the U.S. military and intelligence agencies have bet on heavily. The first Predator carrying weapons was rushed to Afghanistan just four days after the Sept. 11, 2001, terrorist attacks. Today, the Air Force is spending nearly $3 billion a year buying and operating drones, and is training pilots to fly more unmanned than manned aircraft. Demand is so strong that even non-pilots such as civil engineers and military police are being trained.
More than 7,000 drones of all types are in use over Iraq and Afghanistan. The planes have played an integral part in the offensive now being carried out in Marja, Afghanistan, by U.S. Marines and British and Afghan troops.
The Pentagon has adapted consumer-driven technology such as satellite television and digital video to give pilots, combat troops and commanders at headquarters a real-time look at the enemy on computer screens. For the first time in warfare, troops on the ground can see the enemy miles away on live video feeds.
Drone strikes in Pakistan are part of a separate CIA program that has killed more than two dozen senior Al Qaeda and Taliban figures, including two leaders of the Pakistani Taliban in the last six months.
But the attacks also kill civilians, inflaming the sentiment that the United States is fighting an undeclared, illegal war from the skies over that country. Some critics say the problems are so serious that the entire program is counterproductive and should be shut down.
This is combat in the age of video games and virtual reality. Even though drone pilots operate from half a world away, they are as engaged in deadly combat as any pilot inside an airplane.
A drone pilot can fire on an insurgent dug into the Afghan hills and be home in time for a backyard barbecue. In just an hour or two, the pilot can go from a heated argument with a spouse to a tense radio conversation with an amped-up soldier pinned down by weapons fire.
"On the drive out here, you get yourself ready to enter the compartment of your life that is flying combat," said retired Col. Chris Chambliss, who until last summer commanded drone operations at Creech Air Force Base, the command center for seven Air Force bases in the continental U.S. where crews fly drones over Iraq and Afghanistan. "And on the drive home, you get ready for that part of your life that's going to be the soccer game."
Drone crews don't put their lives at risk. Instead, they juggle vast streams of video and data. With briefings both before and after their missions, their workdays typically stretch to 10 or 11 hours. Many of the pilots are experienced military fliers, but the camera operators tend to be much younger -- often only 19 or 20, and new to the stresses of combat.
Just like troops in Iraq or Afghanistan, drone crews have access to chaplains, psychologists and doctors. They are taught to keep an eye on one another for signs of stress.
The psychological challenges are unique: Pilots say that despite the distance, the video feed gives them a more intimate feel for the ground than they would have from a speeding warplane. Some say they would prefer to be in Afghanistan or Iraq to avoid the daily adjustment from the soccer field to the battlefield.
After his stint in Nevada flying drones, which the military refers to as "remotely piloted aircraft," Nelson recently transferred to a crew at an air base in Kandahar, Afghanistan.
Crews there and in Iraq, often battling high winds and freezing temperatures, control the drones on takeoff and landing, then hand them off to the U.S.-based teams.
While still in Nevada, after arriving for his shift on a mild day bathed in brilliant sunshine, Nelson received a battlefield briefing and then opened the door to his office -- the ground control station. He settled into the cockpit seat, known to pilots as the "Naugahyde Barcalounger," facing computer screens displaying live images from the mountains of Afghanistan -- color during the day, black-and-white at night.
As in any other cockpit, he had readouts for engine speed and temperature, altitude, fuel, pitch and roll angles, as well as other flight data.
At his fingertips were two keyboards. He could type messages in chat rooms connecting him to scores of military personnel and analysts worldwide, and he could call up maps, satellite images and intelligence reports. He talked by radio with ground commanders and troops who saw the same live images on their laptops and hand-held radios.